The major objective of this research is to study the epidemiology of chronic lymphocytic leukemia (CLL), focusing upon possible associations with sources of chronic antigenic stimulation, occupations and familial factors. A second objective is to define possible HLA associations with CLL. To accomplish these objectives, the study will be divided into three components. In Part I all new cases of CLL first diagnosed in Baltimore SMSA from June, 1969 through May, 1979 will be identified. Medical chart review of all these cases and two groups of matched controls will be performed. Part II will consist of an interview study of all cases and controls, identified in Part I, who are still alive. For cases and controls who have died or are lost to follow-up, a mailed questionnaire will be sent to next-of-kin, spouse or closest friend. Part III has three components, all involving HLA testing. These components include an HLA case-control study, a prospective HLA study of "rapidly progressive" versus "indolent" cases of CLL and HLA testing of families with two or more cases of CLL, lymphoproliferative diseases and/or autoimmune diseases.